1. Field Of The Invention
The present invention relates generally to perforating systems for perforating a well bore, and more particularly to perforating systems for use with capsule type shaped charges.
2. Description Of The Prior Art
The problem addressed by the present invention is that of passing a perforating gun through a restricted downhole opening, and then properly locating the perforating means of the gun substantially adjacent the well bore after the perforating gun reaches the portion of the well bore which is to be perforated.
Prior art approaches to solving this problem have been very different from the present invention.
One manner in which the prior art has addressed this problem is through the use of a "swing jet" arrangement wherein the charges are pivotally connected to a housing so that the charges may be vertically oriented for passage downward through a restricted opening; then a mechanical arrangement swings the charges through an angle of 90.degree. to rotate the forward ends of the charges outward closer to the well bore to be perforated. Such arrangements are shown in U.S. Pat. Nos. 2,912,930, 2,543,814, 2,924,173, 2,947,253, 2,990,774, 3,067,678, 3,067,679, 3,107,611, 3,107,612 and 3,116,689.
While the swing jet arrangement does provide a solution to the problem described above, it does so through a rather complex mechanical actuating mechanism.
A second approach found in the prior art is the use of an eccentric kickover spring arrangement so that the perforating gun is pushed off center to one side of the well bore to form a single vertical row of perforations along only one side of the well bore. One such arrangement is shown in U.S. Pat. No. 3,707,195. Another such arrangement has been marketed by the Dresser Atlas Division of Dresser Industries, Inc., under the same Silver Jet.SM..
Although these eccentric kickover springs are to some extent less mechanically complicated than the swing jet arrangement, they suffer from the very severe limitation of only providing a single row of perforations along one side of the well bore. It is much preferable to have circumferentially spaced perforations all the way around the well bore.